Introduction to Anatomy

PR  Ashalatha; G  Deepa

PART 1 ANATOMY

1Section A: General Anatomy

Introduction to Anatomy
Primary Tissues
Special Connective Tissues
Nervous Tissues
Muscle Tissues
Lymphoid Tissues
Skin and its Appendages

Introduction to AnatomyCHAPTER 1

▪ Introduction
▪ Medical and Anatomical Terminology
- • The Anatomical Position
- • The Anatomical Planes
▪ Terms
- • Terms of Relationship
- • Terms of Movement
- • The Meaning of Terms
▪ Approaches in Studying Anatomy
- • Regional Anatomy or Topographical Anatomy
- • Systemic Anatomy
- • Clinical Anatomy
- • Gross Anatomy and Histology
- • Anatomical Variations

INTRODUCTION

Anatomy is the study of structure and function of the body. Aristotle (384–322 BC) was the first person to use the term “anatome”, a Greek word meaning “cutting up or taking apart”. The Latin word “dissecare” has a similar meaning.

Anatomy is one of the oldest basic medical sciences; it was first studied formally in Egypt. Human Anatomy was taught in Greece by Hippocrates (460–377 BC) who is regarded as the “Father of Medicine”. He has written several books on Anatomy.

MEDICAL AND ANATOMICAL TERMINOLOGY

Although students entering the new world of Medicine are familiar with the common terms for many parts and regions of the body (e.g. heart, brain, liver, lung), they should learn to use the internationally adopted nomenclature, the Nomina Anatomica.

Anatomical terminology is important because it introduces the student to a large part of Medical Terminology. Since most terms are derived from Latin and Greek, medical language can be difficult at first, but as the student learns the origin of medical terms, the words make sense.

Example: Levator palpebrae superioris muscle

Clear communication is fundamental in Clinical Medicine. To describe the body clearly and to indicate the position of its parts and organs relative to each other, Anatomists and Clinicians use the same descriptive terms of position and direction.

The Anatomical Position (Fig. 1.1)

All descriptions in Human Anatomy and Clinical Medicine are expressed in relation to “Anatomical Position”.

A person in the anatomical position is standing erect (or lying supine) with the head, eyes and toes directed forward, the upper limbs by the sides with the palms facing anteriorly. The student must always visualize the anatomical position in his “mind's eye” when describing patients lying on their backs, sides or fronts. Always describe the body as if it were in the anatomical position.4

Fig. 1.1: Anatomical position

The Anatomical Planes

Anatomical descriptions are also based on four imaginary planes that pass through the body in the anatomical position. They are as follows:

Median
Sagittal
Coronal
Horizontal

The Median Plane (Fig. 1.2)

This is the imaginary vertical plane passing longitudinally through the body from front to back, dividing it into right and left halves.

The Sagittal Planes

These are parallel to the median plane. They are named after the sagittal suture of the skull (Fig. 1.3). The sagittal plane that passes through the median plane can be called the midsagittal plane; those passing parallel to the midsagittal plane and away from the median plane may be called the parasagittal planes.

The Coronal Planes

These are imaginary vertical planes passing through the body at right angles to the median plane, dividing it into anterior (front) and posterior (back) portions. These planes are named after the coronal suture of the skull, which is in a coronal plane (Fig. 1.3).

Fig. 1.2: Median plane

Fig. 1.3: Skull—viewed from above, showing sagittal and coronal sutures

The Horizontal Planes

These are imaginary planes passing through the body at right angles to both the median and coronal planes (They are parallel to the “horizon”). A horizontal plane divides the body into superior (upper) and inferior (lower) parts. A horizontal plane is also referred to as the transverse plane (Fig. 1.4).5

Fig. 1.4: Horizontal or transverse plane

TERMS

Terms of Relationship (Table 1.1)

Various terms (adjectives) are used to describe the relationship of parts of the body in the Anatomical Position.

Terms of Movement (Fig. 1.5, Table 1.2)

Various terms are used to describe the different movements of the limbs and other parts of the body. Movements take place at joints where two or more bones meet or articulate with one another.

The Meaning of Terms

Most of the anatomical terms are derived from Greek and Latin. Some of them are translated to English (e.g. musculus = muscle). Many anatomical terms indicate the shape, size, location and function or resemblance of a structure to something.

Examples

According to shape
1. Deltoid – delta or triangular
2. Sphenoid – wedge-shaped
3. Styloid – pillar-shaped
4. Uvula – grape-like
5. Pisiform – Pea-shaped
According to the number of heads of origin
1. Biceps – 2 heads
2. Triceps – 3 heads
3. Quadriceps – 4 heads

Table 1.1 Commonly used terms of relationship and comparison

No.	Term	Meaning	Example
1.	Superior (cranial)	Nearer to the head	The lung is superior to the diaphragm
2.	Inferior (caudal)	Nearer to the feet (tail)	The stomach is inferior to the heart
3.	Anterior (ventral)	Nearer to the front	Cornea is anterior to the lens
4.	Posterior (dorsal)	Nearer to the back	Lens is posterior to the cornea
5.	Medial	Nearer to the median plane	Heart is medial to the lung
6.	Lateral	Away from the median plane	Kidney is lateral to the vertebral column
7.	Proximal	Nearer to the trunk or point of origin	The knee is proximal to the ankle
8.	Distal	Farther from the trunk or away from the origin	The wrist is distal to the elbow
9.	Superficial	Nearer to the surface	Muscles of the thigh are superficial to the bone femur
10.	Deep	Farther from the surface	The femur is deep to the muscles of thigh
11.	External (outer)	Towards the exterior	The sclera is the external coat of the eyeball
12.	Internal (inner)	Towards or in the interior	Retina is internal to the sclera and choroid
13.	Central	Nearer or toward the center	Brain is a part of the central nervous system
14.	Peripheral	Farther or away from the center	The spinal nerves are part of the peripheral nervous system
15.	Parietal	Pertaining to the external wall of a body cavity	Parietal peritoneum lines the abdominal wall
16.	Visceral	Pertaining to the covering of an organ	Visceral pleura covers the external surface of lung

Table 1.2 Commonly used terms of movement

No.	Term	Meaning	Example
1.	Flexion	Bending or decreasing the angle between body parts	Flexing the elbow joint
2.	Extension	Straightening or increasing the angle between body parts	Extending the knee joint
3.	Abduction	Moving away from the median plane	Abducting the upper limb
4.	Adduction	Moving toward the median plane	Adducting the lower limb
5.	Rotation	Moving around the long axis	Medial and lateral rotation of UL
6.	Circumduction	Circular movement combining flexion, extension, abduction and adduction	Circumduction of upper limb e.g. bowling
7.	Eversion	Moving the sole of the foot away from the median plane
8.	Inversion	Moving the sole of the foot toward the median plane	e.g. As if to remove the thorn
9.	Supination	Rotating the forearm and hand laterally, palm faces anteriorly Radius lies parallel to ulna	e.g. When a person extends a hand to beg
10.	Pronation	Rotating the forearm and hand medially so that palm faces posteriorly. Radius crosses ulna diagonally	e.g. Patting a child on the head
11.	Protrusion	Moving anteriorly	Sticking the chin out
12.	Retrusion or retraction	Moving posteriorly	Tucking the chin
13.	Elevation	To lift	Elevation of eyeball to look upwards
14.	Depression	To lower	Depression of eyeball to look at the feet

According to function

For example,
1. Depressor anguli oris – Muscle which depresses the angle of mouth
2. Tensor tympani – Muscle which tenses the tympanic membrane
According to size
1. Gluteus maximus – Largest among the gluteus muscles
2. Gluteus minimus – Smallest among the gluteus muscles
According to length
1. Abductor pollicis longus – Long abductor of thumb
2. Abductor pollicis brevis – Short abductor of thumb
According to consistency
- Pancreas – Pan = throughout; Kreas = Flesh; fleshy throughout
- Dura mater – Dura = tough; Mater = mother; Tough mother
According to location
1. Biceps brachii – Biceps muscle of arm
2. Biceps femoris – Biceps muscle of thigh
3. Triceps suri – 3 muscles of calf
According to sites of attachment

For example,
1. Sternocleidomastoid muscle – attached to sternum, clavicle and mastoid
2. Omohyoid; omos = shoulder

Omohyoid – from scapula (shoulder blade) to hyoid.

Some of the commonly used anatomical and clinical abbreviations are given in Table 1.3.

APPROACHES IN STUDYING ANATOMY

The three main approaches are as follows:

Regional Anatomy
Systemic Anatomy
Clinical Anatomy

Regional Anatomy or Topographical Anatomy

It is the study of the body by regions such as head, neck, thorax, abdomen and limbs.

Systemic Anatomy (Table 1.4)

It is the study of the body systems, e.g. digestive system, cardiovascular system, nervous system.7

Fig. 1.5: Movements

Clinical Anatomy

Correlation of anatomy with clinical signs and symptoms to arrive at a diagnosis.

Gross Anatomy and Histology

Gross Anatomy

It is the examination of body structures that can be seen without a microscope.

Histology

Microscopic study of a tissue.

Table 1.3 Commonly used anatomical and clinical abbreviations

a, aa	Artery, arteries
ANS	Autonomic nervous system
A-V	Atrioventricular
C₁-C₇(C₈)	First to seventh cervical vertebrae or 1st to 8th spinal nerves
Ca	Cancer, carcinoma
CAD	Coronary artery disease
CAT or CT	Computerized axial tomography
CN	Cranial nerve
CNS	Central nervous system
CSF	Cerebrospinal fluid
ECG	Electrocardiogram
EEG	Electroencephalogram/graphy
G; GK	Greek
GI / GIT	Gastrointestinal/gastrointestinal tract
IP	Interphalangeal
V	Interventricular or intervertebral
V	Intravenous
IVC	Inferior vena cava
IVF	In vitro fertilization
Jt	Joint
L₁ - L₅	1st to 5th Lumbar Nerves/vertebrae
LA	Left atrium
LICS	Left Intercostal space
Lig	Ligament
LP	Lumbar puncture
LV	Left ventricle
m, mm	Muscle, muscles
MCP	Metacarpophalangeal
MI	Myocardial Infarction
MRI	Magnetic resonance imaging
MTP	Medical Termination of Pregnancy
MV	Mitral valve
n, nn	Nerve, nerves
PA	Posteroanterior
PNS	Peripheral nervous system, paranasal sinuses
RA	Right atrium
RV	Right ventricle
S₁-S₅	First to fifth sacral vertebrae/nerves
SA	Sinuatrial/sinoatrial
SVC	Superior vena cava
T₁-T₁₂	1st to 12th thoracic vertebrae/nerves
TIA	Transient ischemic attack
TMJ	Temporomandibular joint
V, VV	Vein/veins

Table 1.4 Systems and their branches of study

No.	System	Organ/Organs studied	Branch of study
1.	Integumentary system	Skin	Dermatology
2.	The skeletal system	Bones and cartilages	Osteology
3.	The articular system	Joints and ligaments	Arthrology
4.	The muscular system	Muscles	Myology
5.	The nervous system	Central and peripheral nervous system	Neurology
6.	The circulatory system/cardiovascular system	Heart, blood vessels and lymphatics	Angiology/Cardiology
7.	The digestive system	Digestive tract and glands assisting digestion	Gastroenterology
8.	The respiratory system	Air passages and lungs	Pulmonology
9.	The urinary system	Kidneys, ureters, bladder and urethra	Urology
10.	The reproductive or genital system	Genital organs—male or female	Female – Gynecology Male – Andrology
11.	The endocrine system	Ductless glands, e.g. Thyroid, pituitary	Endocrinology

Anatomical Variations

Individuals differ in physical appearance. Similarly variations are seen in the size, shape, weight, origin, course and termination of various organs, arteries, nerves and veins. So, individual variation must be considered while examining a patient and in the diagnosis and treatment of that patient.

Chapter Notes

Introduction to AnatomyCHAPTER 1